Input Capacitor

Shaz · 20th September 2003, 02:51 PM

I recently built an IGC based on Peter's design and am very pleased with the results. The sound is really very good and it has a good amount of power. There was one problem I encountered that I was hoping others might be able to shed some light on.

My amp uses the recommended 4.7 uF bipolar input cap. I noticed that the overall performance was excellent including very acceptable bass response and very open and clear high frequencies. However, there was a "fuzziness" in a very narrow midrange band (affecting tenor voices and instruments in the same range). I tried shorting the input caps and that appeared to eliminate the problem. I was wondering what others have experienced with different values and types of the input cap. Also, what is the purpose of the input cap?

tschrama · 20th September 2003, 04:53 PM

I've had good results with a LM3886 inverted GainClone without input cap.... I sounded good, low offset (about 25mV), everything was fine ... untill ... one sad day ... I messed up the powersupply of my preamp .. without realizing that, I switched on the amp ... a big oemmpfffff ... no sound .. until after a minute or so, while I was trying to find what was wrong, suddenly a weird kind of smell appeared and smoke was coming out of my reflex ports ... my woofers where toasted.... a input cap would probably have saved my woofers.. it limits DC-gain to 1...

Goodluck to you

,
Thijs

analog_sa · 20th September 2003, 05:03 PM

Quote:

a input cap would probably have saved my woofers.. it limits DC-gain to 1...

It certainly limits DC gain to zero

So you pre was also DC coupled? Now, that's brave.

tschrama · 20th September 2003, 06:39 PM

Ehhhhhhh it limits DC gain to zero!! sorry about that ... you were right analog_sa .... yeehhhhhh I was brave, young and stupid... and got some ideas in my head about low frequency group delay etc ect .... actually the preamp was capacitor coupled, but I used it a headphone amp too, so I used a 4700uF output cap ... this had a DC time of 300 seconds or so .. hmmmm stupid... but I've learned.. my newest gainclone uses a 4.7uF input cap ... and it sounds good..too

Regards,
Thijs

20th September 2003, 02:51 PM	#1
Shaz diyAudio Member Join Date: Jul 2003 Location: Colorado	Input Capacitor I recently built an IGC based on Peter's design and am very pleased with the results. The sound is really very good and it has a good amount of power. There was one problem I encountered that I was hoping others might be able to shed some light on. My amp uses the recommended 4.7 uF bipolar input cap. I noticed that the overall performance was excellent including very acceptable bass response and very open and clear high frequencies. However, there was a "fuzziness" in a very narrow midrange band (affecting tenor voices and instruments in the same range). I tried shorting the input caps and that appeared to eliminate the problem. I was wondering what others have experienced with different values and types of the input cap. Also, what is the purpose of the input cap?

Thread Tools	Search this Thread
Show Printable Version Email this Page	Search this Thread: Advanced Search

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
Input capacitor	Triox	Solid State	45	19th May 2013 06:00 AM
Input Capacitor	otherside	Chip Amps	26	20th January 2010 03:32 PM
5u4g input capacitor	alexg	Tubes / Valves	4	4th June 2009 05:33 AM
input Capacitor, what will work best?	pjpoes	Parts	7	31st January 2005 03:10 AM
P3A Amp: Input Capacitor C1	dine1967	Solid State	4	3rd February 2003 12:46 AM

New To Site?	Need Help?
Register to Participate Search Privacy Statement Contact Us	Frequently Asked Questions Did you forget your password? Mark Forums Read


	Please consider donating to help us continue to serve you. Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving

20th September 2003, 04:53 PM	#2
tschrama diyAudio Member Join Date: Jul 2001 Location: The Netherlands	I've had good results with a LM3886 inverted GainClone without input cap.... I sounded good, low offset (about 25mV), everything was fine ... untill ... one sad day ... I messed up the powersupply of my preamp .. without realizing that, I switched on the amp ... a big oemmpfffff ... no sound .. until after a minute or so, while I was trying to find what was wrong, suddenly a weird kind of smell appeared and smoke was coming out of my reflex ports ... my woofers where toasted.... a input cap would probably have saved my woofers.. it limits DC-gain to 1... Goodluck to you , Thijs

20th September 2003, 06:39 PM	#4
tschrama diyAudio Member Join Date: Jul 2001 Location: The Netherlands	Ehhhhhhh it limits DC gain to zero!! sorry about that ... you were right analog_sa .... yeehhhhhh I was brave, young and stupid... and got some ideas in my head about low frequency group delay etc ect .... actually the preamp was capacitor coupled, but I used it a headphone amp too, so I used a 4700uF output cap ... this had a DC time of 300 seconds or so .. hmmmm stupid... but I've learned.. my newest gainclone uses a 4.7uF input cap ... and it sounds good..too Regards, Thijs